Efficiency of Drug Resistance Genotypic Tests in Specimens with Low HIV Viral Load

The early recognition of resistance to antiretroviral agents could allow a rapid switch in therapy and therefore avoid the accumulation of mutations and reduce the risk of cross-resistance. However, the efficiency of genotypic tests in specimens with low viral load (VL) is severely compromised since human immunodeficiency virus (HIV) RNA in these samples often goes unrecognized. The frequency of results provided by a line probe assay (LiPA, Murex), a commercially available drug resistance test and a home-made point mutation assay (PMA) for recognizing the codon 151 multidrug-resistance mutation was examined in 664 plasma samples stratified with respect to VL values. Overall, 421 (63%) samples could be interpreted by both LiPA and PMA. The sensitivity decreased as plasma VL lowered: 89% for samples with VL >10000 HIV RNA copies/ml, 77% for those with VL between 500 and 10000 HIV RNA copies/ml and 37% for specimens with VL <500 HIV RNA copies/ml. A good agreement existed comparing the sensitivity of the home-made PMA and LiPA. Although the former tends to produce more results, the difference did not achieve statistical significance. Our results support that new, more sensitive, HIV RNA extraction methods need to be implemented for the rapid recognition of drug-resistant mutants in patients experiencing an early rebound in plasma viraemia.

A rapid non-culture-based assay for clinical monitoring of phenotypic resistance of human immunodeficiency virus type 1 to lamivudine (3TC)

Monitoring for lamivudine (3TC) resistance is important both for the clinical management of human immunodeficiency virus type 1 (HIV-1)-infected patients treated with 3TC and for surveillance of transmission of 3TC-resistant HIV-1. We developed a novel non-culture-based assay for the rapid analysis of phenotypic resistance to 3TC of HIV-1 in plasma. The assay measures the susceptibility of HIV-1 reverse transcriptase (RT) activity to 3TC triphosphate (3TC-TP) in plasma. RT detection was done by the Amp-RT assay, an ultrasensitive PCR-based RT assay. Under our assay conditions, we found that 5 microM 3TC-TP inhibited RT activity from wild-type (WT), zidovudine-resistant, or nevirapine-resistant HIV-1 but not from HIV-1 carrying either the M184V mutation or multidrug (MD) resistance mutations (77L/116Y/151M or 62V/75I/77L/116Y/151M). Mixing experiments showed a detection threshold of 10% 3TC-resistant virus (M184V) in a background of WT HIV-1. To validate the assay for the detection of phenotypic resistance of HIV-1 to 3TC in plasma samples, HIV-1 RT in 30 plasma specimens collected from 15 patients before and during therapy with 3TC was tested for evidence of phenotypic resistance by the Amp-RT assay. The results were compared with those of genotypic analysis. The RT in 12 samples was found to be 3TC sensitive, while the RT in 18 samples had evidence of phenotypic resistance. All 12 samples with 3TC-sensitive RT had WT genotypes at codon 184 and were retrieved before treatment with 3TC. In contrast, all 18 specimens with 3TC-resistant RT were posttherapy samples. This assay provides a simple, rapid, and reliable method for the detection of phenotypic resistance of HIV-1 to 3TC in plasma.

CCR5 genotype and HIV-1 infection in perinatally-exposed infants

The CCR5 chemokine receptor is required by non-syncytium HIV-1 strains to infect target cells. A 32 base pair deletion (delta32) in the CCR5 gene causes a structural CCR5 modification that does not permit HIV-1 entry into cells. The rate of the CCR5 delta32 was investigated in 137 children born from HIV-infected mothers. Overall, five (10.6%) of 47 HIV-infected infants showed the defect in heterozygosis vs. eight (8.9%) of 90 uninfected children. No CCR5 delta32 homozygotes were found. Interestingly, among infected children, five (21.7%) of 23 showing a slow disease progression were heterozygous for the CCR5 delta32, meanwhile none of the 24 infants with rapid disease course had the deletion (P = 0.022). In conclusion, the CCR5 delta32 defect does not protect against vertical HIV-1 transmission, but is associated with a delayed disease progression in HIV-infected children.

Impact of chronic liver disease due to hepatitis viruses as cause of hospital admission and death in HIV-infected drug users

The life expectancy of HIV-positive individuals has been prolonged in recent years, as a consequence of the wide use of antiretroviral drugs and primary prophylaxis for the most common opportunistic infections. In HIV-positive persons infected parenterally, chronic viral liver disease (CVLD), mainly that caused by hepatitis C virus (HCV), is frequently seen. Moreover, chronic hepatitis C seems to present a more accelerated course in HIV-infected patients, leading to cirrhosis and liver failure in a shorter period of time. The aim of the present study was to investigate the impact of CVLD on the morbidity and mortality of HIV-positive patients. A retrospective analysis of the causes of hospital admission during a 4.5-year period in a reference centre for AIDS situated in Madrid was performed. Decompensated liver disease (encephalopathy, ascites, jaundice), or complications directly related to it (gastrointestinal bleeding, hepatorenal syndrome, peritonitis) were diagnosed in 143 (8.6%) of 1670 hospital admissions. These episodes of CVLD corresponded to 105 different individuals, a quarter of whom had two or more re-admissions. HCV alone or in combination with other hepatotropic viruses was involved in 93 (88.6%) patients admitted for CVLD. Death directly associated with CVLD occurred in 15 individuals, which represented 4.8% of the total causes of inhospital mortality during the study period, and represented the fifth cause of death in hospital for HIV-infected patients. In conclusion, CVLD represents an important cause of hospital admission and death in HIV-infected drug users.

Prevalence of drug resistance mutations in Spain among both naive and pretreated patients

The ERASE Spanish Study Group was founded in 1997 with the primary objective of monitoring both the prevalence and impact of the development of resistance to antiretroviral drugs in HIV-infected sentinel populations. Two major studies, one in 1997 and another in 1998, have been conducted so far. Global data and results derived from substudies are summarized in this presentation.

Analysis of pol gene heterogeneity, viral quasispecies, and drug resistance in individuals infected with group O strains of human immunodeficiency virus type 1

Nucleotide sequences of the reverse transcriptase (RT) coding region have been compared in four new human immunodeficiency virus type 1 (HIV-1) group O isolates. Phylogenetic analysis of this pol region highlights a cluster of these four HIV-1 group O sequences with seven other group O isolates (5% intracluster nucleotide sequence diversity) similar to clusters classified as subtypes in HIV-1 group M (an average of 4.9% intrasubtype sequence diversity). Based on these analyses, this group O cluster has been designated subtype A-O. A longitudinal study of a heterosexual couple infected with group O (ESP1 and ESP2) allowed a detailed analysis of RT sequences (amino acids 28 to 219). Directed evolution and a slightly higher mutation frequency was observed in the RT sequences of patient ESP2, treated with antiretroviral drugs, than that from the untreated patient ESP1. Antiretroviral treatment also selected for specific substitutions, M184V and T215Y in the RT coding region, conferring resistance to 3'-dideoxy-3'-thiacytidine and zidovudine, respectively. A Gly98 to Glu RT substitution identified in the treated patient suggests a possible reversion of a nonnucleoside RT inhibitor-resistant phenotype. Using RT clones from this longitudinal study, both heteroduplex tracking assay and cloning-sequencing techniques were employed for an extensive genetic analysis of pol gene quasispecies. Amino acid substitutions (i.e., Phe-77 to Leu, Lys-101 to Glu, and Val-106 to Iso) associated with antiretroviral resistance were identified in RT clones from HIV-1 group O-infected patients not subjected to drug therapy or treated with unrelated drugs. Finally, phylogenetic relationships between RT clones of the treated ESP2 patient and those of the untreated ESP1 patient show how drug pressure can direct evolution of viral pol gene quasispecies independently of direct drug-resistant substitutions.

[7 new cases of HIV-2 infection recognized in Madrid in 1996 and 1997]

The infection with human immunodeficiency virus type-2 (HIV-2) is endemic in Western Africa, where it is responsible for many of AIDS cases. In Spain, 72 cases with HIV-2 until December 1997 had been reported, mainly in African immigrants. Seven of these cases (4 males and 3 females) were identified during 1996 and 1997. Five came from Western Africa and other two were Spanish, one from Alicant and the other from Vigo. Only one out of the seven patients presented clinical manifestations (Pneumocystis carinii pneumonia); the remaining patients were asymptomatic. Viral isolates from six of these patients were genetically characterized: three were subtype A, whereas those from Equatorial Guinea patients corresponded to HIV-2 subtype B.

LTR and tat variability of HIV-1 isolates from patients with divergent rates of disease progression

The genetic heterogeneity and transcription activity of the human immunodeficiency virus type 1 (HIV-1) LTR region and tat gene have been examined. Comparison involved the relevant genomic regions of viruses isolated from twenty long-term survivors and from ten typical progressors. No significant differences were observed in mutation frequencies among the two groups, although there was a significant higher proportion of synonymous substitutions in the tat gene of viruses from typical progressors. Four LTR sequences showed an insertion of 20-31 residues at the junction between the LTR Nef-coding and the LTR noncoding region. Neither these insertions nor other genetic changes found in these sequences affected the LTR transcription function, as measured in transient expression assays using transfection of both established cell lines and peripheral blood lymphocytes with plasmid DNA. The results did not allow the association of structural or functional alterations in LTR or tat with a degree of disease progression. The results reinforce the concepts of complexity of HIV-1 evolution in infected individuals, and the multifactorial nature of progression to AIDS.

Tropism, coreceptor use, and phylogenetic analysis of both the V3 loop and the protease gene of three novel HIV-1 group O isolates

HIV-1 has been subdivided into two groups, M and O, based on phylogenetic analysis. To better understand the pathogenesis of group O viruses, we studied biologic and genetic characteristics of two primary isolates from Spain, ES1158.1 and ES1159.1, and one from the United States, MD.1. After viral isolation, we studied the replication kinetics in peripheral blood mononuclear cells (PBMCs) and macrophages, as well as in different cell lines. All three isolates could replicate in both PBMCs and macrophages. Because no syncytium formation was detected in the MT-2 cell line, viruses were classified as non-syncytium inducing (NSI). All three isolates used the CCR5 coreceptor for entry into the human osteosarcoma (HOS) CD4 cells. Phylogenetic analysis of V3 loop sequences showed that ES1158.1 and ES1159.1 isolates were closely related to the ANT70 strain, whereas MD.1 isolate clustered with the MVP-5180 strain in the same branch. Interestingly, all viruses appeared to be more closely related to the MVP-5180 strain when the protease gene was analyzed, although accessible sequences of this region are very limited.